WO2022183527A1 - Complex-structure carbon fiber-sic whisker-reinforced sisic composite material and preparation method therefor - Google Patents

Abstract

A complex-structure carbon fiber-SiC whisker-reinforced SiSiC composite material and a preparation method therefor. The preparation method comprises the following steps: (a) fully mixing silicon carbide, chopped carbon fibers and thermoplastic phenolic resin to obtain a SiC-Cf mixed powder; (b) subjecting the SiC-Cf mixed powder to 3D printing forming to obtain a SiC-Cf green body; (c) infiltrating the SiC-Cf green body with a SO2-C slurry, and then carrying out a first heat treatment to obtain a SiCw-SiC-Cf blank containing SiC whiskers; (d) infiltrating the SiCw-SiC-Cf blank with a polycarbosilane organic solution, and then carrying out a second heat treatment to obtain a second blank; and (e) densifying the second blank by using a siliconizing process. The prepared carbon fiber-SiC whisker-reinforced SiSiC composite material has excellent mechanical properties, and is suitable for use in the field of equipment such as a thermal protection system of a hypersonic aircraft, a hot end component of an aero-engine and a high-performance brake pad.

Description

A complex structure carbon fiber-SiC whisker reinforced SiSiC composite material and preparation method 【Technical field】

The invention belongs to the field of reaction sintered silicon carbide preparation, and more particularly relates to a complex-structure carbon fiber-SiC whisker reinforced SiSiC composite material and a preparation method.

【Background technique】

With the rapid development of science and technology in the fields of aerospace, automotive, space optics, etc., its core components, such as hypersonic aircraft thermal protection systems, aero-engine hot-end components, high-performance braking systems and space mirrors, have more and more requirements for material properties. Harsh. SiC ceramic matrix composites are expected to be successfully applied in the above fields due to their excellent properties such as low density, high thermal conductivity, ablation erosion resistance and wear resistance. However, SiC ceramics have high brittleness and high crack sensitivity, and their inherent difficulty in machining restricts the formation of this material into complex structural parts, which greatly limits its application range. For SiC ceramic materials with complex structures, traditional processing methods have the problems of complex processes and high manufacturing costs. For example, the molding process of obtaining the green body by molding or cold isostatic pressing, and then processing it into the desired shape with the aid of numerical control machine equipment (CNC) relies heavily on the processing capacity of CNC. The components of honeycomb structure) are expensive to process, and sometimes it is even difficult to meet the design requirements. Although ceramic wet molding techniques including grouting, gel injection molding, and direct solidification molding, which have been widely used in recent years, can be used to prepare complex structures, these methods all require the help of molds, which are costly for small batch production. High, not suitable for personalization. In addition, the ceramic wet molding technology needs to prepare a slurry with high solid content and good fluidity first, and the actual solid content of the slurry is difficult to exceed 70wt%, so it is difficult to avoid certain conditions in the later curing, degreasing and sintering stages of the green body. The degree of shrinkage, the geometric accuracy of the sample is relatively low.

3D printing (additive manufacturing) is listed as an advanced manufacturing technology that needs to be developed to enhance national competitiveness and meet future challenges. Among them, selective laser sintering (SLS) and 3DP printing are represented by powder bed based additive manufacturing. Material manufacturing technology has brought new possibilities for the rapid and efficient formation of large and complex ceramic composites. As a branch of 3D printing technology, technologies such as SLS and 3DP are suitable for the rapid manufacture of composite materials with complex structures and special shapes, and can meet the rapid prototyping manufacturing requirements of various ceramic parts such as whole and separate parts; Setting the support structure simplifies the post-processing procedure of the formed parts, which is expected to solve the difficult problems faced in the preparation of SiC ceramic matrix composites with complex structures. In recent years, there have been relevant reports on the use of 3D printing to form SiC materials. For example, CN200510020015.5 discloses a preparation method of laser sintering rapid prototyping SiC ceramics. The complex-shaped SiC ceramic is obtained by processing, but the SiC powder used in this method needs to be sprayed and granulated to ensure good fluidity, which makes the cost of raw materials required by this method high and the preparation process is cumbersome.

For SiC ceramic matrix composites, a major disadvantage is the poor toughness of the material, which limits the reliability of parts made from this type of material. Carbon fiber is an important one-dimensional reinforcing material, which has achieved great success in improving the mechanical properties of traditional ceramic matrix composites. However, due to the adverse effect of fiber on the powder coating performance, it is less directly applied to 3D printing based on powder bed laying. On the other hand, the technology of in-situ synthesis of one-dimensional ceramic reinforcement phase to achieve fiber/whisker/nanowire toughening of materials has been studied in the fields of porous ceramics and carbon composite refractories, but combining this technology with 3D printing Combinations to make fiber/whisker toughened complex-shape SiC ceramics have not received much attention.

[Content of the invention]

In view of the above shortcomings and/or improvement needs of the prior art, the present invention provides a complex structure carbon fiber-SiC whisker reinforced SiSiC composite material and a preparation method. In the present invention, a complex-shaped SiC-C _f green body is formed by using a 3D printing technology, uniformly distributed SiC whiskers are generated inside the body by means of an in-situ synthesis technology, and densification is realized by combining a silicon infiltration process. The SiSiC material obtained by this method contains two reinforcing phases, C _f and SiC _w , so it has excellent mechanical properties, and is especially suitable for high-end composite materials such as hypersonic aircraft thermal protection systems, aero-engine hot-end components, and high-performance brake pads. manufacturing.

For achieving the above object, according to an aspect of the present invention, a preparation method of a complex structure carbon fiber-SiC whisker reinforced SiSiC composite material is provided, comprising the steps:

(a) fully mixing silicon carbide SiC, chopped carbon fiber C _f , and thermoplastic phenolic resin to obtain a SiC-C _f mixed powder;

(b) 3D printing the SiC-C _f mixed powder to obtain a SiC-C _f green body;

(c) impregnating the SiC-C _f green body with SiO ₂ -C slurry, and then heat treatment for the first time to obtain a SiC _w -SiC-C _f body containing SiC whiskers SiC _w , the SiO ₂ -C slurry It is a mixed system of SiO ₂ , C and organic solvent;

(d) impregnating the SiC _w -SiC-C _f green body with a polycarbosilane organic solution, and then heat treatment for the second time to obtain a second green body;

(e) densifying the second green body by a silicon infiltration process, and finally obtaining the complex-structure carbon fiber-SiC whisker-reinforced SiSiC composite material.

Preferably, the particle size distribution of SiC in the SiC-C _f mixed powder described in step (a) is as follows: the particle size of 0.1-10 μm accounts for 0-2wt% of the total SiC powder, and the particle size of 10-25 μm accounts for the total SiC powder 22-35wt% of the SiC powder, and the particle size of 25-150μm accounts for 63-78wt% of the total SiC powder.

Preferably, 3D printing is performed in step (b) to form one of laser selective area sintering and 3DP.

Preferably, the preparation method of the SiO ₂ -C slurry described in step (c) is as follows: selecting amorphous silica, using nano carbon black as raw material, using water or ethanol as dispersion liquid, and using wet ball milling to make it fully mixed , after drying, grinding and crushing to obtain SiO ₂ -C composite powder, and then mixing the SiO ₂ -C composite powder with an organic solvent to obtain SiO ₂ -C slurry.

Preferably, the method of infiltrating the SiO ₂ -C slurry in step (c) is vacuum infiltration or pressure infiltration.

Preferably, the conditions for the first heat treatment in step (c) are vacuum or argon atmosphere or helium atmosphere, the temperature is 1300°C to 1600°C, and the temperature is kept for 3 to 6 hours.

Preferably, the polycarbosilane infiltration in step (d) is vacuum infiltration or pressure infiltration.

Preferably, the conditions for the second heat treatment in step (d) are an inert atmosphere or a reducing atmosphere, the inert atmosphere is an argon atmosphere or a helium atmosphere, the temperature is 1100°C to 1400°C, and the temperature is kept for 1 to 4 hours.

Preferably, the silicon infiltration process in step (e) is as follows: laying metal silicon particles on the bottom of the second green body, heating to 1500°C to 1700°C while vacuuming, holding for 1 to 6 hours, and cooling down.

According to another aspect of the present invention, a complex-structure carbon fiber-SiC whisker-reinforced SiSiC composite material is also protected, which is prepared by the aforementioned preparation method.

The beneficial effects of the present invention are:

1. Compared with the prior art, the preparation method of a complex structure carbon fiber-SiC whisker reinforced SiSiC composite material proposed by the present invention is vacuum-impregnated with SiO ₂ -C slurry obtained by 3D printing and forming, The in-situ synthesis technology enables the formation of uniformly distributed SiC whiskers in the material. Finally, a complex structure carbon fiber-SiC whisker-reinforced SiSiC composite material is obtained by liquid-phase silicon infiltration. The in-situ synthesis technology is used to generate SiC whiskers in the material to avoid It solves the problem that the direct introduction of SiC whiskers/fibers is difficult to disperse uniformly, and the mechanical mixing leads to the damage of the SiC whisker/fiber structure;

2. The chopped carbon fibers of the present invention and the SiC whiskers generated in situ form nano-micron cross-scale synergistic toughening, which is better than the toughening effect of single carbon fibers or SiC fibers as a reinforcing phase, and can greatly improve the material. brittleness.

3. The carbon fiber-SiC whisker-reinforced SiSiC composite material prepared based on the method provided by the present invention has excellent mechanical properties, and is suitable for high-end high-end such as hypersonic aircraft thermal protection systems, aero-engine hot-end components, and high-performance brake pads. It has broad application prospects in the field of equipment.

Description of drawings

FIG. 1 is a morphological diagram of the complex-shaped carbon fiber-SiC whisker-reinforced SiSiC composite prepared in Example 1. FIG.

Figure 2 is based on the SEM test images of _SiCw -SiC- _Cf containing SiCw whiskers after step (c) of Example 1 and Comparative Example 1, wherein (a), (b), (c) in Figure 2 It is the test chart under the scale of 400 microns, 50 microns and 40 microns of Example 1; (d), (e) and (f) in Figure 2 are the scales of 400 microns, 50 microns and 40 microns of Comparative Example 1. test chart.

FIG. 3 is the XRD diffraction pattern of the SiSiC composite material prepared in Example 1. FIG.

【Detailed ways】

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments.

Example

In this embodiment, the SiO ₂ -C slurry is prepared by the following method:

Amorphous silica and nano carbon black are selected as raw materials, water or ethanol is used as dispersion liquid, wet ball milling is used to make them fully mixed, and after drying, they are ground and crushed to obtain SiO ₂ -C composite powder, and then SiO ₂ -C The composite powder is mixed with kerosene in a mass ratio of 1:8 to obtain SiO ₂ -C slurry.

Example 1

(a) using SiC, C _f , and thermoplastic phenolic resin as raw materials, and fully mixing to obtain a SiC-C _f mixed powder; the specific characteristics of SiC in the SiC-C _f mixed powder are: powder with a particle size of 10-25 μm The SiC powder accounts for 22 wt % of the total SiC powder, and the powder with a particle size of 25-150 μm accounts for 78 wt % of the total SiC powder.

(b) using the above-mentioned SiC-C _f mixed powder to carry out laser selective sintering to obtain a SiC-C _f green body;

(c) The SiC-C _f green body was infiltrated with SiO ₂ -C slurry. After drying, the green body was placed in a corundum crucible for heat treatment at 1600°C in an Ar atmosphere and kept for 3 hours to obtain a SiC _w -SiC-C _f sample.

(d) The SiC _w -SiC-C _f sample was impregnated with an organic solution of polycarbosilane (PCS), then heated at 1400 °C for 1 h in an Ar atmosphere.

(e) The sample obtained in the previous step is densified by the siliconizing process, the siliconizing temperature is 1700°C, the temperature is kept for 1 h, and the complex structure carbon fiber-SiC whisker reinforced SiSiC composite material is obtained by cooling with the furnace. FIG. 1 is a morphological diagram of the complex-shaped carbon fiber-SiC whisker-reinforced SiSiC composite prepared in Example 1. FIG.

Example 2

(a) Using silicon carbide (SiC), chopped carbon fiber (C _f ) and thermoplastic phenolic resin as raw materials, and fully mixing to obtain a SiC-C _f mixed powder; the specific characteristics of SiC in the SiC-C _f mixed powder The powders with a particle size of 10-25 μm account for 25 wt % of the total SiC powder, and the powder with a particle size of 25-150 μm accounts for 75 wt % of the total SiC powder.

(b) using the above-mentioned SiC-C _f mixed powder to carry out 3DP forming to obtain a SiC-C _f green body;

(c) The SiC-C _f green body was infiltrated with SiO ₂ -C slurry, dried and placed in a corundum crucible for heat treatment at 1500 °C under vacuum conditions, and kept for 4 h to obtain a SiC _w -SiC-C _f sample.

(d) The SiC _w -SiC-C _f sample was impregnated with an organic solution of polycarbosilane (PCS), and then heated at 1300 °C for 2 h in a CO atmosphere.

(e) The sample obtained in the previous step is densified by the siliconizing process, the siliconizing temperature is 1650°C, the temperature is kept for 1.5h, and the complex structure carbon fiber-SiC whisker reinforced SiSiC composite material is obtained with the cooling of the furnace.

Example 3

(a) Using silicon carbide (SiC), chopped carbon fiber (C _f ) and thermoplastic phenolic resin as raw materials, and fully mixing to obtain a SiC-C _f mixed powder; the specific characteristics of SiC in the SiC-C _f mixed powder It is as follows: the powder with a particle size of 0.1-10 μm accounts for 1 wt% of the total SiC powder, the powder with a particle size of 10-25 μm accounts for 28 wt% of the total SiC powder, and the powder with a particle size of 25-150 μm accounts for the total SiC powder. 71 wt%.

(b) using the above-mentioned SiC-C _f mixed powder to carry out laser selective sintering to obtain a SiC-C _f green body;

(c) The SiC-C _f green body was infiltrated with SiO ₂ -C slurry, dried and placed in a corundum crucible for heat treatment at 1400 °C under vacuum conditions, and kept for 5 h to obtain a SiC _w -SiC-C _f sample.

(d) The SiC _w -SiC-C _f sample was impregnated with an organic solution of polycarbosilane (PCS), then heated at 1200 °C for 3 h in an Ar atmosphere.

(e) The sample obtained in the previous step is densified by the silicon infiltration process, the silicon infiltration temperature is 1600 ° C, the temperature is kept for 2.0 h, and the complex structure carbon fiber-SiC whisker reinforced SiSiC composite material is obtained with the furnace cooling and cooling.

Example 4

(a) Using silicon carbide (SiC), chopped carbon fiber (C _f ) and thermoplastic phenolic resin as raw materials, and fully mixing to obtain a SiC-C _f mixed powder; the specific characteristics of SiC in the SiC-C _f mixed powder The powders with a particle size of 10-25 μm account for 32 wt % of the total SiC powder, and the powder with a particle size of 25-150 μm accounts for 68 wt % of the total SiC powder.

(b) using the above-mentioned SiC-C _f mixed powder to carry out 3DP forming to obtain a SiC-C _f green body;

(c) The SiC-C _f green body was infiltrated with SiO ₂ -C slurry, and after drying, it was placed in a corundum crucible under Ar atmosphere for heat treatment at 1300 °C and kept for 6 h to obtain a SiC _w -SiC-C _f sample.

(d) The SiC _w -SiC-C _f sample was impregnated with an organic solution of polycarbosilane (PCS), then heated at 1100 °C for 4 h in an Ar atmosphere.

(e) The sample obtained in the previous step is densified by the silicon infiltration process, the silicon infiltration temperature is 1550°C, the temperature is kept for 2.5h, and the complex structure carbon fiber-SiC whisker reinforced SiSiC composite material is obtained with the furnace cooling and cooling.

Example 5

(a) Using silicon carbide (SiC), chopped carbon fiber (C _f ) and thermoplastic phenolic resin as raw materials, and fully mixing to obtain a SiC-C _f mixed powder; the specific characteristics of SiC in the SiC-C _f mixed powder The powders with a particle size of 0.1-10 μm account for about 2 wt% of the total SiC powder, the powder with a particle size of 10-25 μm accounts for 35 wt% of the total SiC powder, and the powder with a particle size of 25-150 μm accounts for the total SiC powder. 63wt%.

(b) using the above-mentioned SiC-C _f mixed powder to carry out laser selective sintering to obtain a SiC-C _f green body;

(c) The SiC-C _f green body was infiltrated with SiO ₂ -C slurry, dried and placed in a corundum crucible under Ar atmosphere for heat treatment at 1450 °C for 4.5 h to obtain a SiC _w -SiC-C _f sample.

(d) The SiC _w -SiC-C _f sample was impregnated with an organic solution of polycarbosilane (PCS), then heated at 1350 °C in a CO atmosphere and kept for 2.5 h.

(e) The sample obtained in the previous step is densified by the silicon infiltration process. The silicon infiltration temperature is 1500°C, and the temperature is kept for 3.0h.

Comparative Example

Comparative Example 1

The difference between this example and Example 1 is that in step (c), after cleaning the surface of the SiC-C _f green body, without impregnating the SiO ₂ -C slurry, it is directly placed in an oven to dry at 110°C; The corundum crucible was heat-treated at 1600°C under Ar atmosphere and kept for 3h.

Comparative Example 2

The difference between this embodiment and Embodiment 1 is that there is no step (d).

Test Example

1. Mechanical properties test. For the samples obtained in Examples 1, 2 and Comparative Examples 1 and 2, the mechanical properties of the materials were tested, and the results are shown in Table 1. The flexural strength was measured by the three-point bending method according to the ASTM C1161-18 standard, and the fracture toughness was measured by the unilateral notched beam method according to the ASTM C1421-18 standard.

Table 1 Example mechanical properties test result table

Example	Flexural strength/MPa	Fracture toughness/MPa m 0.5
Example 1	260	3.5
Example 2	245	3.8
Comparative Example 1	189	2.3
Comparative Example 2	195	2.5

It can be seen from Table 1 that the flexural strength and fracture toughness of the SiSiC composites prepared in Examples 1 and 2 provided by the present invention are significantly improved compared with those prepared in Comparative Example 1 and Comparative Example 2, which proves that the present invention provides The method can prepare SiSiC composites with better mechanical properties.

2.SEM test.

Figure 2 is a SEM test image of _SiCw -SiC- _Cf containing SiCw whiskers prepared in step (3) of Example 1 and Comparative Example 1, wherein (a), (b), (c) in Figure 2 is the secondary electron morphology of the obtained sample fracture at different scales in Example 1; (d), (e), (f) in Figure 2 are the ports of the sample obtained in Comparative Example 1 observed at different scales Secondary electron morphology.

It can be seen from Fig. 2 that, because of the "cleaning powder on the surface of the SiC-C _f green body" in Comparative Example 1, the SiO ₂ -C slurry was not infiltrated, and it was directly placed in an oven to dry at 110 °C; and then placed in a corundum crucible with Ar Heat treatment at 1600 °C under the atmosphere and hold for 3 h”, no SiC whiskers were formed inside the sample. However, in Example 1, the SiC-C _f green body was impregnated with SiO ₂ -C slurry in advance, so that the SiO ₂ -C composite powder in sufficient contact entered the interior of the body material. During the heat treatment process at 1600℃, saturated SiO _x vapor was locally formed around the SiO ₂ -C composite powder, and then SiC whiskers were formed in the internal pores of the green body by reaction.

This result proves that the method provided by the present invention is a necessary condition for in-situ generation of a large number of SiC whiskers inside the material.

3. XRD test.

FIG. 3 is an XRD test chart of the SiSiC composite material prepared in Example 1. FIG. The test method is as follows: the SiSiC composite material obtained in Example 1 is first treated with acid to remove residual silicon, then washed with deionized water, dried, then crushed and fully ground through a 325 mesh sieve, and finally the obtained powder is subjected to powder X-ray diffraction.

It can be seen from Figure 3 that the SiSiC composite material prepared in Example 1 contains two SiC phases, namely α-SiC (corresponding to the SiC particles added in advance in the raw material) and β-SiC (corresponding to the SiC whiskers generated in situ), It is proved that the method provided by the present invention can successfully prepare the SiSiC composite material containing SiC whiskers.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (10)

1. A preparation method of a complex structure carbon fiber-SiC whisker reinforced SiSiC composite material is characterized in that, comprising the following steps:

   (a) fully mixing silicon carbide SiC, chopped carbon fiber C _f , and thermoplastic phenolic resin to obtain a SiC-C _f mixed powder;

   (b) 3D printing the SiC-C _f mixed powder to obtain a SiC-C _f green body;

   (c) impregnating the SiC-C _f green body with SiO ₂ -C slurry, and then heat treatment for the first time to obtain a SiC _w -SiC-C _f body containing SiC whiskers SiC _w , the SiO ₂ -C slurry It is a mixed system of SiO ₂ , C and organic solvent;

   (d) impregnating the SiC _w -SiC-C _f green body with a polycarbosilane organic solution, and then heat treatment for the second time to obtain a second green body;

   (e) densifying the second green body by a silicon infiltration process, and finally obtaining the complex-structure carbon fiber-SiC whisker-reinforced SiSiC composite material.
2. The preparation method according to claim 1, wherein the particle size distribution of SiC in the SiC-C _f mixed powder in step (a) is as follows: the particle size of 0.1-10 μm accounts for 0-2wt of the total SiC powder %, the particle size of 10-25 μm accounts for 22-35 wt% of the total SiC powder, and the particle size of 25-150 μm accounts for 63-78 wt% of the total SiC powder.
3. The preparation method according to claim 1, characterized in that, in step (b), 3D printing is performed to form one of laser selective area sintering and 3DP.
4. The preparation method according to claim 1, wherein the preparation method of the SiO ₂ -C slurry in step (c) is: selecting amorphous silica, nano carbon black as raw material, and using water or ethanol as The dispersion liquid is fully mixed by wet ball milling, and after drying, it is ground and crushed to obtain SiO ₂ -C composite powder, and then the SiO ₂ -C composite powder is mixed with an organic solvent to obtain SiO ₂ -C slurry.
5. The preparation method according to claim 4, wherein the method of infiltrating the SiO ₂ -C slurry in step (c) is vacuum infiltration or pressure infiltration.
6. The preparation method according to claim 4, wherein the conditions of the first heat treatment in step (c) are vacuum or argon atmosphere or helium atmosphere, the temperature is 1300℃～1600℃, and the temperature is kept for 3～6h.
7. The preparation method according to claim 1, wherein the polycarbosilane infiltration in step (d) is vacuum infiltration or pressure infiltration.
8. The preparation method according to claim 7, wherein the condition of the second heat treatment in step (d) is an inert atmosphere or a reducing atmosphere, the inert atmosphere is an argon atmosphere or a helium atmosphere, and the temperature is 1100 ℃～1400℃, keep warm for 1～4h.
9. The preparation method according to claim 1, wherein the silicon infiltration process in step (e) is as follows: the bottom of the second body is flattened with metal silicon particles, and heated to 1500°C to 1700°C while vacuuming, Keep warm for 1 to 6 hours, and then cool down.
10. A complex structure carbon fiber-SiC whisker reinforced SiSiC composite material is characterized in that, it is prepared according to the preparation method of any one of claims 1 to 9.

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